The invention relates to a multi-lumen catheter and more particularly, to a multi-lumen catheter having a deformable separating wall between adjacent lumina.
A double-lumen catheter, which consists of a tube which is rigid in its cross-section, in which an additional thinner tube, with a rigid cross-section, proceeds in a "side by side" manner, which tube is firmly connected with the internal wall of the outer tube, is already known from the publication "Medcomp" of the firm Medical Components, Inc., of 14999 Delp Drive, Harleysville, Pa. 19438, U.S.A., page 4. One lumen is formed between the inner and the outer tube, while the second lumen is formed within the inner tube. An additional double-lumen catheter, which is constructed on the basis of the same principle as the first-described catheter, but in which the inner tube proceeds loosely and coaxially in the outer tube, however, is also depicted and described on page 6 of the said "Medcomp" publication.
Catheters of the type under discussion, which consist of a tube which is flexible over its length, but is, however, essentially rigid in its cross-section, and which proceed in three independent lumina, are already known from the publication WO 8810128-A, as well as through the publication "CERTOFIX DUO/TRIO" of the firm B. Braun, of Melsungen AG in D-3508, Melsungen.
There is a strong need, within the field of medicine, for multi-lumen catheters in order to be able to introduce incompatible medications through a single catheter separately from one another, and also, furthermore, in order to make a parallel infusion possible, both by means of gravity, as well as by means of a pump. All of the catheters described above have a relatively large diameter, since their total cross-section essentially corresponds to the sum of the individual cross-sections of the individual lumina. Because of the greater cross-section as well as the cross-pieces separating the individual lumina from one another within the interior of the catheter, a greater rigidity also arises, because of the increased resistance moment. There additionally exists the disadvantage that the stiffening which is brought about from the cross-pieces between the lumina negatively influences the bending behavior of the catheter, at least in a number of directions of bending. For this reason, the wall thicknesses of such multi-lumen catheters must be greater than is the case with single-lumen catheters. In addition, the flow resistance is increased in the lumina, since the wall surface is increased relative to a round, single-lumen catheter. This applies, in particular, for the known catheters which have been described above, in which the lumen, which is formed between the inner and the outer tube, has a disproportionately large circumferential surface. Flow resistance is, as is known, essentially determined by the size of the circumferential surface.
One additional disadvantage of the multi-lumen catheter described above consists of the fact that, as statistics show, the risk to patients is increased with their use. The large diameter, which makes a relatively larger puncture necessary, and which, within a vessel, constricts the cross-section of the same, is, above all, responsible for this. In addition, because of the increased bending stiffness, bending forces are conveyed to the puncture opening and to the vessel to a greater extent.
The task which forms the basis of the invention is that of creating a catheter of the type under discussion which has at least two lumina, the cross-sections of which are reduced in relation to the known types of multi-lumen catheters, and the bending resistance of which is reduced, and in which, furthermore, the risk for the patients is reduced.
The task which forms the basis of the invention is solved by means a multi-lumen catheter incorporating a separating wall between lumina that is deformable.
The invention is based on the basic idea that the individual lumina of a multi-lumen catheter are not, or must not, be simultaneously used with their full through-flow capacity. Within a circumferential area which is essentially rigid in its cross-section, and which, as is the case with a one-lumen, tube-shaped catheter, ensures the desired handling, the cross-section of the single-lumen is variable. This is brought about through the fact that the separating wall between both of the lumina is expansible and/or deformable within the transverse plane. By this means, it is possible to increase the cross-section within a lumen, by means of pressure, which is increased relative to the other lumen or to the other lumina, at the expense of the other lumen or the other lumina. The same then applies for the other lumen, or for the other lumina. In a three-lumen catheter, additional possibilities result in which, for example, two lumina can increase their cross-section at the expense of the third lumen, or vice versa. In catheters with still more lumina, additional possibilities for variation result.
Because of their expandability and/or deformability, the separating walls either do not increase the resistance moment of the entire catheter, or else they only do so to a non-significant extent. By this means, the characteristics and the manipulation relative to the simplest and most favorable form of a catheter--that is to say, of a tube--remain practically unchanged. The manipulation is correspondingly simple for the physician, and the risk for the patient is slight.
The inner separating wall between the individual lumina can have any desired form of implementation. In one embodiment, the separating wall forms an internal tube which proceeds within an external tube, which forms the circumferential area of the catheter which is essentially rigid in its cross-section. If the lumen is stressed, by means of a fluid with pressure, between the internal tube and the external tube, then the internal, deformable and flexible tube collapses, either in part or in whole, so that the lumen extends, between the internal tube and the external tube, over practically the entire internal width of the external tube. If the internal tube is stressed with a fluid which is under pressure which is greater than the pressure between the internal tube and the external tube, then the internal tube expands over its entire cross-section. If the internal tube is not only flexible--which is the case in a thin, but tension-proof material--but also expandable, then, under the corresponding pressure stressing of the internal tube, its cross-section can expand to the internal cross-section of the external tube. In this case, the entire internal cross-section of the external tube is, in an extreme case, available for both of the variable lumina.
In the embodiment stated above, the internal tube can proceed loosely in the external tube. The internal tube can, however, also be partially connected with the external tube. Several internal tubes can also proceed simultaneously within the external tube.
In another form of implementation of the basic idea in accordance with the invention, the separating wall extends diametrically or as secant, in an essentially round tube forming the circumferential area which is rigid in its cross-section, and is longer than the diameter or the secant. This essentially applies for the event that the cross-piece is less expandable than it is deformable. Since it is longer than the diameter or the secant, it assumes, if no pressure is applied, any form which is desired, such as, for example, a coiled or arced shape. Upon application of pressure in one lumen (or with an increased pressure relative to the other lumen), the cross-piece deforms in the sense of an enlargement of the pressure-stressed lumen and assumes--in the extreme case--depending on its length, a shape in which it is applied to the internal wall of the external tube, so that the lumen which is not stressed with pressure is, consequently, essentially made to disappear.
In yet another form of implementation of the present invention the separating wall has at least three partial separating walls, which proceed together in a star-like shape, and thus form at least three lumina. If the partial separating walls are thereby extended, then they should consist of an expandable material. It is appropriate, however, if they are, in a manner similar to the above-stated form of implementation, longer than the direct connecting line between their common, central connecting point and the connecting point on the external circumference. Without a pressure stressing, they all proceed in an arc-shaped manner, for example, or else the arc which is either without pressure, or which is under the lower pressure, can, under the influence of the lumen which has the greater pressure stressing on it, bend outwardly.
The distal end of the catheter can essentially be constructed in any form which is desired. In the form of implementation in which the separating wall forms an internal tube, this is connected, at the distal end of the catheter, suitably tightly joined with the preferably thinned external end of the outer tube, and an aperture is located in the external tube and at a distance from the distal end. In this manner, the distal apertures of both of the lumina replaced at a distance from one another, which is particularly appropriate for incompatible drugs.
In the forms of implementation, in which the separating wall proceeds diametrically or as a secant, or in which the separating walls proceed essentially radially, it is appropriate that the lumina arc, in the distal end of the catheter, sealed into one, while the sealed lumen, or the sealed lumina, have, at a distance from the distal end of the catheter, preferably at different distances from the same, through-flow apertures through the external circumferential area which is rigid in its cross-section. Even in the case of several lumina, therefore, a separation of the distal opening apertures is possible, in order to thereby be able to spatially separate non-compatible drugs from one another.
For the purpose of the connection of the proximal end of the catheter in accordance with the invention, it is appropriate if the lumina are expanded in their diameter at the proximal end of the catheter, and are provided, within this area, with a connecting piece for the connection of the lumina. In this manner, the lumina are not adversely affected in their diameter by the connecting piece. The expansion of the diameter is suitably brought about by means of an interval extrusion, or by means of the expansion of a heated tool.
For the connection of a catheter in accordance with the invention, in which the separating wall forms a tube in an external tube, it is appropriate that, on the proximal end, the internal tube projects beyond the external tube. Both ends of the tubes are tightly inserted into coaxial recesses of an attachment piece whereby, behind each end of the tubes, a space which can be connected with a connection, or which is connected with a connection, is located.